Made visible by the invisible Van Elewyck, Véronique
Nature physics,
01/2019, Letnik:
15, Številka:
1
Journal Article
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Odprti dostop
Using data from the IceCube telescope, a study presents the first attempt at obtaining geophysical information about Earth’s internal structure from the flux of neutrinos that pass through it.
The study of atmospheric neutrinos crossing the Earth can provide tomographic information on the Earth’s interior, complementary to the standard geophysics methods. This contribution presents an ...updated study of the potential of the KM3NeT-ORCA detector for neutrino oscillation tomography of the Earth, showing that after ten years of operation it can measure the electron density in both the lower mantle and the outer core with a precision of a few percents in the case of normal neutrino mass hierarchy.
Since the measurement of the mixing angle θ13, the determination of the neutrino mass hierarchy has become a central challenge of neutrino physics. Recent studies have pointed out that it could ...reveal itself in the atmospheric neutrino sector, where oscillations are affected by Earth matter effects. This contribution reports on the ORCA feasibility study for such a measurement with an underwater Cherenkov detector based on the technology developed for the KM3NeT neutrino telescope. The baseline performances are discussed for a reference detector with 50 instrumented lines. Preliminary projections, based on the muon channel only, indicate that a 3 - 5σ significance measurement is within reach of a detector with an exposure of the order of 20 Mton years. Further improvement is expected to come from the electron channel, which is currently under study.
KM3NeT-ORCA is a water-Cherenkov neutrino detector designed for studying the oscillations of atmospheric neutrinos, with the primary objective of measuring the neutrino mass ordering. Atmospheric ...neutrinos crossing the Earth undergo matter effects, modifying the pattern of their flavour oscillations. The study of the angular and energy distribution of neutrino events in ORCA can therefore provide tomographic information on the Earth's interior with an independent technique, complementary to the standard geophysics methods. Preliminary estimations based on a full Monte Carlo simulation of the detector response show that after ten years of operation the electron density can be measured with a precision of 3-5% in the mantle and 7-10% in the outer core - depending on the mass ordering.
Many of the astrophysical sources and violent phenomena observed in our Universe are potential emitters of gravitational waves and high-energy cosmic radiation, including photons, hadrons, and ...presumably also neutrinos. Both gravitational waves (GW) and high-energy neutrinos (HEN) are cosmic messengers that may escape much denser media than photons. They travel unaffected over cosmological distances, carrying information from the inner regions of the astrophysical engines from which they are emitted (and from which photons and charged cosmic rays cannot reach us). For the same reasons, such messengers could also reveal new, hidden sources that have not been observed by conventional photon-based astronomy. Coincident observation of GWs and HENs may thus play a critical role in multimessenger astronomy. This is particularly true at the present time owing to the advent of a new generation of dedicated detectors: the neutrino telescopes IceCube at the South Pole and ANTARES in the Mediterranean Sea, as well as the GW interferometers Virgo in Italy and LIGO in the United States. Starting from 2007, several periods of concomitant data taking involving these detectors have been conducted. More joint data sets are expected with the next generation of advanced detectors that are to be operational by 2015, with other detectors, such as KAGRA in Japan, joining in the future. Combining information from these independent detectors can provide original ways of constraining the physical processes driving the sources and also help confirm the astrophysical origin of a GW or HEN signal in case of coincident observation. Given the complexity of the instruments, a successful joint analysis of this combined GW and HEN observational data set will be possible only if the expertise and knowledge of the data is shared between the two communities. This Colloquium aims at providing an overview of both theoretical and experimental state of the art and perspectives for GW and HEN multimessenger astronomy.
► We estimate the gravitational-wave and high-energy neutrino emission window for GRBs. ► GRBs emit gravitational waves and high-energy neutrinos likely within 500
s. ► The derived time window allows ...for a 1000
s window in multimessenger searches. ► The analysis is largely based on model-motivated comparisons with observations.
We derive a conservative coincidence time window for joint searches of gravitational-wave (GW) transients and high-energy neutrinos (HENs, with energies ≳100
GeV), emitted by gamma-ray bursts (GRBs). The last are among the most interesting astrophysical sources for coincident detections with current and near-future detectors. We take into account a broad range of emission mechanisms. We take the upper limit of GRB durations as the 95% quantile of the
T
90’s of GRBs observed by BATSE, obtaining a GRB duration upper limit of ∼150
s. Using published results on high-energy (>100
MeV) photon light curves for 8 GRBs detected by Fermi LAT, we verify that most high-energy photons are expected to be observed within the first ∼150
s of the GRB. Taking into account the breakout-time of the relativistic jet produced by the central engine, we allow GW and HEN emission to begin up to 100
s before the onset of observable gamma photon production. Using published precursor time differences, we calculate a time upper bound for precursor activity, obtaining that 95% of precursors occur within ∼250
s prior to the onset of the GRB. Taking the above different processes into account, we arrive at a time window of
t
HEN
−
t
GW
∈
−500
s,
+500
s. Considering the above processes, an upper bound can also be determined for the expected time window of GW and/or HEN signals coincident with a detected GRB,
t
GW
−
t
GRB
≈
t
HEN
−
t
GRB
∈
−350
s,
+150
s. These upper bounds can be used to limit the coincidence time window in multimessenger searches, as well as aiding the interpretation of the times of arrival of measured signals.
The determination of neutrino mass ordering (NMO) is one of the prime goals of several neutrino experiments. KM3NeT/ORCA and JUNO are two next-generation neutrino oscillation experiments both aiming ...at addressing this question. ORCA can determine the NMO by probing Earth matter effects on the oscillation of atmospheric neutrinos in the GeV energy range. JUNO, on the other hand, is sensitive to the NMO by investigating the interference effects of fast oscillations in the reactor electron antineutrino spectrum at medium baseline. This contribution presents the potential of determining the NMO through a combined analysis of JUNO and ORCA data. When measuring the Δm312 with a wrong ordering assumption, the best-fit values are different between the two experiments. This tension, together with good constraints on the Δm312 measurement by both experiments, enhances the combined NMO sensitivity beyond the simple sum of their sensitivities. The analysis shows that a 5 σ significance is reachable in less than 2 years of data taking with both experiments for true normal neutrino mass ordering, assuming current global best-fit values of the oscillation parameters, while 6 years will be needed for any other parameter set.
The ANTARES detector has been operating continuously since 2007 in the Mediterranean Sea, demonstrating the feasibility of an undersea neutrino telescope. Its superior angular resolution in the ...reconstruction of neutrino events of all flavors results in unprecedented sensitivity for neutrino source searches in the southern sky at TeV energies, so that valuable constraints can be set on the origin of the cosmic neutrino flux discovered by theIceCube detector. The next generation KM3NeT neutrino telescope is now under construction, featuring two detectors with the same technology but different granularity: ARCA designed to search for high energy (TeV-PeV) cosmic neutrinos and ORCA designed to study atmospheric neutrino oscillations at the GeV scale, focusing on the determination of the neutrino mass hierarchy. Both detectors use acoustic devices for positioning calibration, and provide testbeds for acoustic neutrino detection.
Recent results from the ANTARES neutrino telescope Van Elewyck, Véronique
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2014, Letnik:
742
Journal Article
Recenzirano
Odprti dostop
The ANTARES neutrino telescope is currently the largest operating water Cherenkov detector and the largest neutrino detector in the Northern Hemisphere. Its main scientific target is the detection of ...high-energy (TeV and beyond) neutrinos from cosmic accelerators, as predicted by hadronic interaction models, and the measurement of the diffuse neutrino flux. Its location allows for surveying a large part of the Galactic Plane, including the Galactic Centre.
In addition to the standalone searches for point-like and diffuse high-energy neutrino signals, ANTARES has developed a range of multi-messenger strategies to exploit the close connection between neutrinos and other cosmic messengers such as gamma-rays, charged cosmic rays and gravitational waves. This contribution provides an overview of the recently conducted analyses, including a search for neutrinos from the Fermi bubbles region, searches for optical counterparts with the TAToO program, and searches for neutrinos in correlation with gamma-ray bursts, blazars, and microquasars. Further topics of investigation, covering e.g. the search for neutrinos from dark matter annihilation, searches for exotic particles and the measurement of neutrino oscillations, are also reviewed.
In the last 70 years, geophysics has established that the Earth’s outer core is an FeNi alloy containing a few percent of light elements, whose nature and amount remain controversial. Besides the ...classical combinations of silicon and oxygen, hydrogen has been advocated as the only light element that could account alone for both the core density and velocity profiles. Here we show how this question can be addressed from an independent viewpoint, by exploiting the tomographic information provided by atmospheric neutrinos, weakly-interacting particles produced in the atmosphere and constantly traversing the Earth. We evaluate the potential of the upcoming generation of atmospheric neutrino detectors for such a measurement, showing that they could efficiently detect the presence of 1 wt% hydrogen in the Earth’s core in 50 years of concomitant data taking. We then identify the main requirements for a next-generation detector to perform this measurement in a few years timescale, with the further capability to efficiently discriminate between FeNiH and FeNiSi
x
O
y
core composition models in less than 15 years.
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